Block copolyetheresters with poly(trimethylene 2,6-naphthalenedicarboxylate) segments: Effect of composition on thermal properties

Block copolyetheresters with hard segments of poly(trimethylene 2,6-naphthalenedicarboxylate) and soft segments of poly(tetramethylene oxide) were prepared by melt polycondensation of dimethyl 2,6-naphthalenedicarboxylate, 1,3-propanediol and poly(tetramethylene ether)glycol (PTMEG) of molecular weights of 650, 1000 and 2000. The block copolyetheresters were characterized by FTIR, ¹H NMR, DSC, X-ray diffraction, TSC (thermal stimulated current), DMA and TGA. It was found that the thermal transitions were dependent on the composition. As the charge molar ratio of PTMEG to dimethyl 2,6-naphthalenedicarboxylate, x, increased, the T_m and ΔH_m of the polyester segments decreased, which has been also confirmed by the X-ray diffraction data. The polyether segments of the block copolyetheresters derived from PTMEG2000 could crystallize after cooling, but those of the block copolyetheresters derived from PTMEG1000 and PTMEG650 could not crystallize. The DSC, TSC and DMA results show consistent T_g data of the polyether segments. Based on the shift in T_g of the polyether segments, the amorphous parts of the polyether segments and the amorphous parts of the polyester segments were immiscible for the block copolyetheresters derived from PTMEG2000, but became partially miscible for the block copolyetheresters derived from PTMEG1000 and PTMEG650. The TGA results indicated that composition had little effect on thermal degradation under nitrogen.     

Effect of thermal history on properties of block-copolyetheresters with poly(tetramethylene 2,6-naphthalenedicarboxylate) segments

The effect of compression molding on the thermal transitions and crystalline properties of block-copolyetheresters with hard segments of poly(tetramethylene 2,6-naphthalenedicarboxylate) and soft segments of poly(tetramethylene oxide) were investigated by differential scanning calorimetry (DSC), X-ray diffraction, thermal stimulated current (TSC), and dynamic mechanical analysis (DMA). The X-ray diffraction patterns of compression molded samples of the block-copolymers were considerably different from those of the corresponding samples with slow-cooling history. After compression molding, the diffraction peaks were changed completely indicating a different crystalline structure for the polyester segments, and the diffraction peaks became sharper indicating a higher crystallinity. The DSC results also showed that the melting point and crystallinity of the polyester segments were increased after compression molding. The glass transition temperatures of the polyether soft phase and polyester hard phase also were determined by DSC, TSC, and DMA separately with consistent data and were found to be dependent on the content of polyether segments and the molecular weight of the poly(tetramethylene ether)glycol (PTMEG) used. A γ-transition was observed by TSC and DMA and seemed to be independent of the composition and the thermal history. The glass transition temperatures of the polyether soft phase and the polyester hard phase of the block-copolymers derived from PTMEG 650 and PTMEG 1000 shifted to a lower temperature after compression molding possibly because of the partial miscibility between the comprising segments in these two series. The abrupt drop in log G′ in the temperature range of −10–15°C for the block-copolymers derived from PTMEG 2000 was caused by the melting of the polyether segments and indicated that the crystalline properties of the polyether segments could affect their mechanical properties. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1441–1449, 1999     

Block copolyetheresters. V. Low-temperature properties of thermotropic block copolyetheresters

The low-temperature properties of block copolyetheresters with hard segments of poly(alkylene p,p′-bibenzoate) and soft segments of poly(tetramethylene ether) were investigated by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). In the temperature range of −100 to 60°C, two transition temperatures, a glass transition temperature (T_g) and a melting temperature (T_m), were found by DSC and are attributed to the polyether segments. The T_g monitored by DSC of the polyether segments of the block copolyetheresters is around −68°C and independent of the composition and the type of polyester segment. Thus, the amorphous parts of the polyether segments should be immiscible with the amorphous parts of the polyester segments. The polyether segments of the block copolyetheresters exhibit a lower T_m and a lower crystallinity than those of the poly(tetramethylene ether)glycol due to the presence of the polyester segments. The crystallizability of the polyether segments is dependent on the composition to some extent. The DMA data show that the dynamic modulus drops more abruptly around −10 to 15°C, indicating that the mechanical properties may change significantly due to the melting of the polyether segments. © 1996 John Wiley & Sons, Inc.     

Block copolyetheresters

Summary Block copolyetheresters with hard segments of poly (pentamethylene p,p'-bibenzoate) and soft segments of poly (tetramethylene ether) have been prepared by melt polycondensation of dimethyl p,p'-bibenzoate, 1,5-pentanediol and poly(tetramethylene ether) glycol (PTMEG) with molecular weights of 650, 1000 and 2000. The polymer composition is governed by the charge molar ratio (x) of PTMEG to dimethyl p,p'-bibenzoate. The block copolyetheresters with x=0.05, 0.1 and 0.2 display a monotropic smectic phase due to the poly (pentamethylene p,p'-bibenzoate) segments. But the block copolyetheresters with x=0.3 exhibit no liquid crystalline behavior. The molecular weight of the PTMEG used has significant effect on the glass transition temperature and crystallizability of the polyether segments. It can be seen from the glass transition temperature results that the miscibility between amorphous parts of the polyether segments and those of the polyester segments is also dependent on the molecular weight of the PTMEG used.     

Poly(vinyl chloride)–polyol (AB)x block copolymers: Synthesis,characterization, and mechanical properties

Poly(vinyl chloride)–polyol (AB)_x block copolymers have been prepared by the condensation polymerization of low-molecular-weight hydroxy-terminated poly(vinyl chlorides) (PVC) and diisocyanate-capped polyester and polyether diols. The difunctional poly(vinyl chlorides) were synthesized by ozonization of commercial resin followed by metal hydride reduction. The (AB)_x block copolymers, which contained 3000 or 4300 molecular weight PVC block sizes and 1000–2000 molecular weight polyol segments, had a wide range of mechanical properties, depending on overall polymer structure. Tensile strengths ranged from 7.8 to 31.5 MPa, elongations from 125% to 610% and torsional stiffness temperatures (T_f) from 25°C to ?22°C.     

Preparation and properties of highly functional copolyetheresters

Block copolyetheresters with hard segments of poly(trimethylene 2,6‐naphthalene dicarboxylate) and soft segments of poly(tetramethylene ether)glycol 2,6‐naphthalene dicarboxylate were prepared by the melt polycondensation of dimethyl 2,6‐naphthalene dicarboxylate (NDC), 1,3‐propanediol (PD), and poly(tetramethylene ether)glycol (PTMEG) with molecular weights of 1000. The block copolyetheresters were characterized by ¹H‐NMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. The block copolyetheresters synthesized with NDC/PD/PTMEG were more heat resistant than those synthesized with dimethyl terephthalate/PD/PTMEG. The block copolyetheresters synthesized with NDC/PD/PTMEG showed stronger elastoplastic behavior than those synthesized with NDC/1,4‐butanediol/PTMEG. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 139–145, 2003     

Polyester-Polyether Block Copolymers II. Thermal and Mechanical Properties of Poly(hexamethylene terephthalate)/Poly(oxytetramethylene) Block Copolymers

The melting and crystallisation behaviour of crystalline phases in poly (hexamethylene terephthalate)/poly(oxytetramethylene) block copolymers have been investigated in relation to copolymer composition and polyether block molecular weight (m.w.). In contrast to that in corresponding homopolymer blends, the polyester crystallinity in the block polymers is greatly reduced by incorporation of polyether units, though some persists even at low polyester contents. Concomitant changes in the glass transition temperatures show part of the polyester component to form a homogeneous component of the amorphous phase. The mechanical properties change with composition in parallel with the changes in copolymer crystallinity and T_g. Copolymers with 20-60 w % of poly(oxytetramethylene) units of m.w. 2000 are highly extensible elastomers. Those with higher m. w. polyether blocks have higher modulus and strength but suffer a serious loss of properties at 60d?C. The observations are interpreted in terms of a model in which polyester crystallites (and polyether crystallites also, for the higher m. w. polyether blocks) are supported within an amorphous matrix by tie-molecules whose nature changes with the copolymer compositions. The results are compared with those for analogous polyester-polyethers having different structural components.     

Influence of morphology on the properties of segmented block copolymers

A comparison was carried out regarding the structure and properties of segmented block copolymers with either non-crystallisable or crystallisable rigid segments. The flexible segment in the block copolymers was a linear poly(propylene oxide) end capped with poly(ethylene oxide), with a segment molecular weight of 2300 g/mol. The rigid segments were either non-crystallisable or monodisperse crystallisable polyamides of varying lengths. The morphologies were studied by TEM and AFM, the thermal mechanical properties by DMA and the elastic properties by compression set and tensile measurements. A direct comparison was made of segmented block copolymers with either liquid-liquid demixed or crystallised structures. The crystallised amide segments were more efficient in increasing the modulus and improving the elastic properties than the non-crystallisable ones. The copolymers with crystallised structures were transparent, had a low glass transition temperature of the polyether phase and a modulus that was independent of temperature between T_g and T_m. These copolymers also displayed a very low loss factor (tan δ), suggesting excellent dynamic properties. The hard phase in segmented block copolymers should thus preferably be crystalline.     

Synthesis and properties of bio-based thermoplastic polyurethane based on poly (L-lactic acid) copolymer polydiol

The goal of this work is the synthesis of a new kind of bio-based thermoplastic polyurethane (BTPU) based on poly(L -lactic acid) (PLA) and poly(tetramethylene) glycol (PTMEG) segments via chain-extension reaction of dihydroxyl terminated (HO-PLA-PTMEG-PLA-OH) copolymer using hexamethylene diisocyanate (HDI) as a chain extender. Polydiols were synthesized through polycondensation of lactic acid and PTMEG in bulk. The chemical structures and molecular weights of polydiols and BTPUs containing different segment lengths and weight fractions of PLA, were characterized by ¹H-NMR and FTIR. The effects of the structures on the physical properties of BTPUs were studied by means of DSC, SEM, and tensile test; crystallization behavior was characterized by POM. The DSC and SEM results indicate that PLA segment is perfectly compatible with PTMEG segment and the crystallization of BTPU is predominantly caused by PLA segment. Polydiol with lower PLA content shows lower T_g and lower crystallinity. Tensile test shows that the elongation at break of BTPU is above 340% at the composition of PLA/PTMEG = 80/20 (w/w). © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Biodegradability of poly(ethylene terephthalate) copolymers with poly(ethylene glycol)s and poly(tetramethylene glycol)

Poly(ethylene terephthalate) copolymers were prepared by melt polycondensation of dimethyl terephthalate and excess ethylene glycol with 10–40mol% (in feed) of poly(ethylene glycol) (E) and poly(tetramethylene glycol) (B), with molecular weight (MW) of E and B 200–7500 and 1000, respectively. The reduced specific viscosity of copolymers increased with increasing MW and content of polyglycol comonomer. The temperature of melting (T_m), cold crystallization and glass transition (T_g) decreased with the copolymerization. T_m depression of copolymers suggested that the E series copolymers are the block type at higher content of the comonomer. T_g was decreased below room temperature by the copolymerization, which affected the crystallinity and the density of copolymer films. Water absorption increased with increasing content of comonomer, and the increase was much higher for E1000 series films than B1000 series films. The biodegradability was estimated by weight loss of copolymer films in buffer solution with and without a lipase at 37°C. The weight loss was enhanced a little by the presence of a lipase, and increased abruptly at higher comonomer content, which was correlated to the water absorption and the concentration of ester linkages between PET and PEG segments. The weight loss of B series films was much lower than that of E series films. The abrupt increase of the weight loss by alkaline hydrolysis is almost consistent with that by biodegradation.     

Polyester-polyether block copolymers. I. Wide-angle X-ray diffraction studies of poly(hexamethylene terephthalate)/poly(oxytetramethylene) and related block polymers

The crystallisation and orientation of the individual structural components of poly(hexamethylene terephthalate)/poly(oxytetramethylene) block copolymers have been studied by wide-angle X-ray diffraction. The crystallisation behaviour in the unstretched state is determined by the proportions and molecular weights of the polyether blocks. For copolymers containing less than 60 wt% of polyether of m. w. ≯ 2000, only the polyester segments crystallise spontaneously, but with polyether m. w > 2000 two crystalline phases are formed. Similar behaviour was found in block polymers from other readily crystallising polyesters, but with non-crystallising polyesters the polyether segments crystallised spontaneously. Moderate tensile deformation of the block copolymers from polyether of m. w. 2000 leads to the stress-reversible highly oriented crystallisation of the polyether whilst the polyester remains undeformed. At higher extensions, irreversible orientation of the polyester segments occurs. The observations suggest that the polyester and polyether segments form discrete regions since otherwise homogeneous crystallisation should occur.     

Preparation and properties of graft and block copolymers of poly(p-phenylene terephthalamide) with polybutadiene

Graft copolymers of polybutadiene (PBD) onto poly(p-phenylene terephthalamide) (PPTA) were prepared by the nucleophilic substitution of N-metalated PPTA with telechelic PBD having bromide end groups. Block copolymers were synthesized by the condensation reaction of telechelic PBD having acid chloride end groups with amino-group-terminated PPTA. The structure of these copolymers was identified by IR spectra. Graft and block copolymers contained PBD segments up to 85 wt % and 45 wt %, respectively. Thermomechanical analyses (TMA) proved the existence of distinctive primary absorption peak corresponding with T_g of PBD for both graft and block copolymers. The T_g's of both types of the copolymers were further ascertained by the DSC curves. TMA curves suggested that the microphase separation occurred between PPTA and PBD. The incorporation of PPTA segments into PBD increased the decomposition temperature compared with the blend polymer composed of PPTA and PBD with the same composition.     

Blocking of soft segments with different chain lengths and its impact on the shape memory property of polyurethane copolymer

The arrangements, whether block or random type, of the soft segments of polyurethane block copolymers prepared with MDI and two kinds of poly(tetramethylene glycol) (PTMG; MW of 1000 or 2000) in various ratios were compared for possible effects on the physical properties of the copolymers. A long soft segment, PTMG‐2000, was superior in all mechanical properties (strain, stress, and modulus) because a long chain length could provide more motional freedom than a short one (PTMG‐1000) could and therefore was helpful in forming strong interchain attractions among hard segments. Inclusion of more PTMG‐2000 led to a lower T_g and a peak shift in infrared spectra. The arrangement of two soft segments in a block‐type copolymer, a key finding in this study, was controlled by separately synthesizing two prepolymers, each with a different chain length, and connecting two prepolymers in a second step. Random‐type copolymers prepared for purposes of comparison were allowed to react with two PTMGs in one step. Two types of copolymers were compared, and the reason for the differences in the shape memory property are discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1435–1441, 2007     

Dynamic mechanical properties of polyurethane block polymers

The dynamic mechanical properties of polyester and polyether urethane block polymers have been investigated at four frequencies (3.5, 11, 35 and 110 Hz) in the temperature range of — 150 to 200°C. The existence of a two phase structure was demonstrated in these systems by the observation of two major transition regions corresponding to (1) the glass transition temperature (T_g) of the ester or ether soft segments, and to (2) the softening temperature of the aromatic-urethane hard segments. Several secondary relaxations were observed in addition to the two major relaxations. It was possible to assign molecular mechanisms to each of these relaxations. All relaxation phenomena were greatly influenced by the molecular weight of the prepolymer, weight percent of hard segments, and thermal history. An increase in the molecular weight of the prepolymer above 1,000 at constant hard segment content resulted in a semi-crystalline material, which possessed a lower T_g for the macroglycol segments. Annealing to enhance crystallinity increased the T_g of the soft segments, consistent with the usual observation in semicrystalline homopolymers. These findings suggest that the relaxation mechanisms of polyurethane block polymers are not only influenced by the degree of crystallinity, but also by the nature of the domain structure.     

Phase behavior for blends of styrene containing triblock copolymers with poly(2,6-dimethyl-1,4-phenylene oxide)

The extent to which the styrene end-blocks of three commercially available triblock copolymers can mix with a particular poly(2,6-dimethyl-1,4-phenylene oxide) (M_n = 22,600 and M_w = 34,000) or PPO has been examined by investigation of the glass transition behavior of the PPO and polystyrene (PS) portions of the blends using differential scanning calorimetry. Each block copolymer has a butadiene-based mid-block which was hydrogenated for two of these materials, but not the third. The three copolymers differ substantially in overall molecular weight and in molecula weight of the blocks. However, in analogy with the literature on blends of homopolymer polystyrene with styrene-based block copolymers, the molecular weight of the PS block should be the principal factor affecting the phase behavior in the present blends. Mixtures of the PPO with the block copolymers having PS blocks with M = 14,500 (nonhydrogenated midblock) and with M = 29,000 (hydrogenated mid-block) exhibited single composition-dependent T_gs for the hard phase, indicating complete mixing of PS segments with the PPO, for all proportions. On the other hand, the block copolymer having a PS block with M = 7,500 and a hydrogenated mid-block exhibited two separate hard phase T_gs corresponding to an essentially pure PPO phase and a PS-rich phase. For blends of homopolymer PS with styrene-based block copolymers, the similar two-phase behavior of the glassy portion can be readily explained by entropic considerations. For the present case, the favorable enthalpic contribution for mixing PPO and PS is an additional factor which seems to influence the restrictions on molecular weight for complete mixing; however, additional work is needed to develop a more quantitative assessment of this new issue.     

Properties and crystallization kinetics of poly(ether ether ketone)‐co‐poly(ether ether ketone ketone) block copolymers

A series of block copolymers composed of poly(ether ether ketone) (PEEK) and poly(ether ether ketone ketone) (PEEKK) components were prepared from their corresponding oligomers via a nucleophlilic aromatic substitution reaction. Various properties of the copolymers were investigated with differential scanning calorimetry (DSC) and a tensile testing machine. The results show that the copolymers exhibited no phase separation and that the relationship between the glass‐transition temperature (T_g) and the compositions of the copolymers approximately followed the formula T_g = T_g1X₁ + T_g2X₂, where T_g1 and T_g2 are the glass‐transition‐temperature values of PEEK and PEEKK, respectively, and X₁ and X₂ are the corresponding molar fractions of the PEEK and PEEKK segments in the copolymers, respectively. These copolymers showed good tensile properties. The crystallization kinetics of the copolymers were studied. The Avrami equation was used to describe the isothermal crystallization process. The nonisothermal crystallization was described by modified Avrami analysis by Jeziorny and by a combination of the Avrami and Ozawa equations. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1652–1658, 2005     

Water vapor transmission of poly(ethylene oxide)‐based segmented block copolymers

This article discusses the rate of water vapor transmission (WVT) through monolithic films of segmented block copolymers based on poly(ethylene oxide) (PEO) and monodisperse crystallisable tetra‐amide segments. The polyether phase consisted of hydrophilic PEO or mixtures of PEO and hydrophobic poly(tetramethylene oxide) (PTMO) segments. The monodisperse tetra‐amide segments (T6T6T) were based on terephthalate units (T) and hexamethylenediamine (6). By using monodisperse T6T6T segments the crystallinity in the copolymers was high (～ 85%) and, therefore, the amount of noncrystallised T6T6T dissolved in the polyether phase was minimal. The WVT was determined by using the ASTM E96BW method, also known as the inverted cup method. By using this method, there is direct contact between the polymer film and the water in the cup. The WVT experiments were performed in a climate‐controlled chamber at a temperature of 30°C and a relative humidity of 50%. A linear relation was found between the WVT and the reciprocal film thickness of polyether‐T6T6T segmented block copolymers. The WVT of a 25‐μm thick film of PTMO₂₀₀₀‐based copolymers was 3.1 kg m^?2 d^?1 and for PEO₂₀₀₀‐based copolymers 153 kg m^?2 d^?1. Of all the studied copolymers, the WVT was linear related to the volume fraction of water absorbed in the copolymer to the second power. The results were explained by the absorption‐diffusion model. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Enhancing the drawability of a polyester by copolymerization with a second type of crystallizable block

A polyester‐amide segmented block copolymer with short monodisperse amide segments was synthesized along with its neat polyester counterpart. The copolymer, containing 10 wt % amide, displayed a T_g and T_m for the polyester phase as well as a high T_m corresponding to the polyamide. The high‐melting amide segments enhanced the dimensional stability of the copolymer and also considerably increased the crystallization rate of the polyester segments. As compared to the neat polyester, the polyester‐amide block copolymer could be drawn at higher temperatures and to higher draw ratios. The maximum draw ratio for this copolymer was obtained just a few degrees below the melting temperature of the polyester segments, and as a result of these higher draw ratios, the fracture stresses were higher. In conclusion, a short monodisperse amide segment in a polyester‐amide block copolymer increased the crystallization rate of the polyester, enhanced the dimensional stability, allowed a higher maximum draw ratio, and raised the fracture strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and properties of poly(imide siloxane) block copolymers with different block lengths

Several poly(imide siloxane) block copolymers with the same bis(γ‐aminopropyl)polydimethylsiloxane (APPS) content were prepared. The polyimide hard block was composed of 4,4′‐oxydianiline and 3,3′,4,4′‐diphenylthioether dianhydride (TDPA), and the polysiloxane soft block was composed of APPS and TDPA. The length of polysiloxane soft block increased simultaneously with increasing the length of polyimide hard block. For better understanding the structure–property relations, the corresponding randomly segmented poly(imide siloxane) copolymer was also prepared. These copolymers were characterized by FT‐IR, ¹H‐NMR, dynamic mechanical thermal analysis, thermogravimetric analysis, polarized optical microscope, rheology and tensile test. Two glass transition temperatures (T_g) were found in the randomly segmented copolymer, while three T_gs were found in the block copolymers. In addition, the T_gs, storage modulus, tensile modulus, solubility, elastic recovery, surface morphology and complex viscosity of the copolymers varied regularly with increasing the lengths of both blocks. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Segmented copolymers of uniform tetra‐amide units and poly(phenylene oxide) by direct coupling

Segmented copolymers with telechelic poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE) segments and crystallizable bisester tetra‐amide units (two‐and‐a‐half repeating unit of nylon‐6,T) were studied. The copolymers were synthesized by reacting bifunctional PPE with hydroxylic end groups with an average molecular weight of 3500 g/mol and bisester tetra‐amide units via an ester polycondensation reaction. The bisester tetra‐amide units had phenolic ester groups. By replacing part of the bisester tetra‐amide units with diphenyl terephthalate units (DPT), the concentration of tetra‐amide units in the copolymer was varied from 0 to 11 wt%. Polymers were also prepared from bifunctional PPE, DPT, and a diaminediamide (6T6‐diamine). The thermal and thermal mechanical properties were studied by DSC and DMA and compared with a copolymer with flexible spacer groups between the PPE and the T6T6T. The copolymers had a high T_g of 180–200°C and a melting temperature that increased with amide content of 220–265°C. The melting temperature was sharp with monodisperse amide segments. The T_m – T_c was 39°C, which suggests a fast, but not very fast, crystallization. The crystallinity of the amide was ～ 20%. The copolymers are semicrystalline materials with a high T_g and a high T_g/T_m ratio (> 0.8). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 512–518, 2007